Surgeons frequently need to gain access to patients' body cavities to perform various procedures. One way to gain access to such a cavity is to perform invasive surgery where the cavity is opened fairly widely from the exterior to allow the surgeon ready access to the interior of the cavity. For example, in most traditional heart surgery, the patient's sternum is split and the overlying tissue is cut back to allow the surgeon to place both hands inside the chest cavity.
Increasingly, however, less invasive techniques are being employed to permit access to body cavities. For example, endoscopic examinations are being used to explore body cavities without having to directly visually inspect them. Gall bladder surgery is also being done increasingly by gaining access to the abdominal cavity through smaller access ports through the abdominal wall rather than using more invasive approaches. (See, for example, U.S. Pat. No. 5,375,588, issued to Yoon).
Increasingly, surgeons are gaining access to the thoracic cavity by passing surgical instruments into the cavity through the intercostal spaces between a patient's ribs. For example, U.S. Pat. No. 5,613,937 (Garrison et al., the teachings of which are incorporated herein by reference) suggests a method of conducting closed-chest heart surgery by passing surgical implements through a number of ports positioned in the intercostal spaces. This patent shows one access cannula which provides an oblong opening which allows a surgeon to pass a replacement valve into the thoracic cavity for placement in the patient's heart.
A wide variety of surgical retractors are also known in the art. Most surgical retractors are intended to allow a surgeon to forcibly urge tissue out of the way to enable unfettered access to the underlying anatomical structures. Most common tissue retractors have a pair of blades which are designed to be inserted into the incision in the patient's tissue and spread laterally apart from one another to expand the incision. These blades commonly take the place of relatively flat paddles which are simply inserted into the incision. Some researchers have proposed using a somewhat curved blade in the interest of reducing trauma to the tissue. For example, O'Neill et al., U.S. Pat. No. 5,512,038, proposed a variety of curved blade designs having varying degrees of complexity. These blades are attached to a standard retraction system employed for back surgery and may be swapped out with other blades to provide the desired shape for any given procedure. In U.S. Pat. Nos. 5,788,630 and 5,931,778, Furnish suggests articulatible blades having an angled configuration. In use, each blade abuts a patient's ribs with their angled surface.
U.S. Pat. No. 4,726,356, issued to Santilli et al., shows a thoracic retractor having a pair of cuffs. Both of these cuffs have a curved contour and are said to engage the sides of the chest incision to permit access to the internal organs. Lenox et al. discloses another retractor in U.S. Pat. No. 5,865,731. FIGS. 5-9 illustrate a retractor having repositionable blades, each of which has a pair of C-shaped grips.
Such prior art retractors tend to cause undue trauma to the tissue and increase the risk of damage to the nerves. This is particularly acute when the tissue retractors are used adjacent a hard, bony structure such as a patient's ribs. Tissue tends to get pinched between the hard blades of the retractor and the hard, bony structure. As a result, the brunt of the force applied against the tissue to widen the incision tends to be borne by a fairly localized area of the tissue. This causes significant trauma to the affected tissue and any structure included within that tissue. For example, any vessels passing through the tissue which is subjected to the increased stress can be traumatized, leading to hematomata adjacent the site. Any nerves passing through this area of the tissue can also experience long-term damage, some of which may never be fully recovered.
The use of curved retractor blades may help address this issue, but they are not believed to provide an effective solution. If the contours of the curved blades were to precisely match the contours of the bony structure with the overlying tissue, this may effectively distribute the force of the retractor blade over a larger area and help minimize A trauma to the issue. As a practical matter, though, a mass-produced retractor blade simply cannot precisely match the contour of each and every patient's body structures. Even if the blade did match the shape of the rib initially upon insertion, the rib will tend to bend somewhat and change its orientation as the ribs are spread apart from one another, leading to a poor fit between the blade and the rib. As a consequence, significant trauma to the tissue adjacent an incision is common even when surgical retractors with curved blades are used.